Process of extracting lubricating oils



May 8, 1934. 1. ROSENBERG PROCESS OF EXTRACTING LUBRICATING OILS Filed Oct. 26, 1952 jynaz Ros enb 6/29 Patented May 8, 1934 UNITED STATES" PATENT oFFicE Ignaz Rosenberg, Berlin, Germany, assignor to the firm Edeleanu Gesellschaft m. b. H., Germany, a German corporation Berlin,

Application October 26, 1932, Serial No. 639,720

' In Germany November 5, 1931 8 Claims.

My invention relates to the refining of mineral oils with hot liquid-S0 Present day practice in the petroleum industry and the requirements of the trade call for the refining of lubricating oil stocks so as to obtain especially high quality lubricating oils. It is highly desirable to obtain lubricating oils having among other improved characteristics, as high a viscosity index as possible, a low Conradson test and a high A. P. I. gravity. I have found that these requirements can be met when. the extraction of raw lubricating oils with liquid sulphur dioxide is effected not at the conventional temperatures ranging from 1 F. to slightly above 32 F., but when treating above room temperatures, say above 85 F. or higher.

Treatment with sulphur dioxide at such high temperatures has heretofore been unknown. Thehighest temperature that was considered possible for the execution of the liquid sulphur dioxide process was around F., corresponding to about room temperature, but preference was always given to much lower temperatures, and no commercial treatments have been efiected so far at room temperature. When applied on heavy hydrocarbon oils, I have found that the liquid sulphur dioxide has a much higher solution power than at lower temperatures without substantially losing its high degree of selectivity. Hot treatment of hydrocarbons with liquid sulphur dioxide becomes thus an ideal refining process for special types of lubricating oils (residual stocks or overhead fractions), upon which the old and conventional liquid sulphur dioxide (Edeleanu) process at low temperatures is not sufliciently efiective. That hot extraction leads to higher quality products than could otherwise be Y obtained, may be seen by the following example:

A California lube oil distillate of A. P. I. gravity 15.3, viscosity index below 0, Conradson carbon 0.51%, was treated with 200% by volume of liquid sulphur dioxide at 25 F., and this treatment resulted in a raflinate of A. P. I. gravity of 21.2, viscosity index 16, Conradson carbon 0.16%, and the yield of refined oil compared to the original'distillate was 62.5% When the same oil was treated at 95 F., instead of 25 F., the A. P. I. gravity of the resulting refined oil was 22.2, the viscosity index 31, Conradson carbon 0.13%, and the yield of refined oil was 48.7%.

Besides better results obtained, the hot extraction process is very flexible, a wide range of treating temperatures being possible. There may be cases where it is advisable to go up to 200 F and higher; in other cases again a high yield of refined oil is more important than a low Conradson carbon or high viscosity index, and a treating temperature of F. may be found to be the most advantageous. g

It may still be added that not only better re- 0 sults are obtained when treating at higher tem-- peratures, but that also the separation of the rafiinate layer from the extract layer in the treating vessel is much quicker than is the case at low temperatures. 5

The apparatus used for hot liquid sulphur dioxide extraction is fundamentally the same as the conventional Edeleanu apparatus. Considerable simplifications, however, are possible, as thef expensive equipment for cooling the distil- 70 late and the liquid sulphur dioxide becomes unnecessary. Furthermore, due to quicker separation of the railinate and extract layer, no setting tanks will be necessary. The new type plant will, therefore, be simpler, require less space and 75 will be more economical.

The accompanying drawing represents a flowsheet of the apparatus which may suitably be used in the operation of the process. The apparatus is similar to that used for cold extraction, but the 0 cooling devices for cooling the oil and the liquid sulphur dioxide have been replaced by heating elements. Also the mixer has to be of a heavier construction due to higher pressure.

The oil to be treated is drawn 01f continuously 35 from a tank not shown here by means of pump (1), forced through heating device (2) and pipe (3) ing) the mixer (4). Pump (7) withdraws sulphur dioxide liquefied in condenser (5) from tank (6), forces it through heating device (8) and pipe (9) into the mixer (4).

In mixer (4) the oil introduced near the bottom ascends while the liquid sulphur dioxide entering near the top descends due to its higher specific gravity. The ascending oil becomes saturated with sulphur dioxide on its upward path and a so-called rafiinate solution leaves the upper part of themixer while a so-called extract solution consisting of liquid sulphur dioxide and the undesirable oil compounds is withdrawn from the bottom of the mixer.

Hot extraction may be carried out under a pressure corresponding to the temperature of the oil and sulphur dioxide mixture and the sulphur dioxide content of it, or under higher than equilibrium pressure. In the first case the pressure in mixer (4) will be somewhat lower than the saturation pressure of the pure liquid sulphur dioxide at the same temperature, e. g. at an extraction temperature of 140 F. the pressure in the mixer would be somewhat lower than 135 lbs. per sq. in. In the second case there is no limit to the pressure; it may be of advantage to choose it so high that the raffinate and extract solutions flow to their respective evaporator without the aid of pumps.

In the plant shown here the first case is assumed. Raflinate solution is continuously drawn off from mixer (4) through pipe by pump (11). and led to heat exchanger (13) through pipe (12). Here, the solution is heated up in counter-current with hot finished rafiinate. Throttling valve (14) reduces the pressure of the solution to the pressure prevailing in evaporator (16) into which it enters after having passed heating element (15). Evaporator (16) is connected with water cooled condenser (5); the pressure in this evaporator must be somewhat higher than the condenser pressure due to fiow resistance in the pipes leading from evaporator to condenser. In evaporator (16) the raffinate is freed from part of its sulphur dioxide and is then led through pipe (1'7) throttling valve (18) and heating element (19) into evaporator (20). In this evaporator a low pressure or a vacuum is maintained by gas pump (50). Under the influence of pressure drop and the increase of temperature practically all the sulphur dioxide is driven out and the finished raifinate leaves evaporator (20) and is forced by pump (21) through pipe (22) and heat exchanger (13) into a finished raffinate tank (not shown).

In a similar way pump (24) causes the extract solution to flow from mixer (4) through pipe (23) and (25) into the extract evaporator group. In heat exchanger (26) the extract solution is preheated by the finished extract before entering the first evaporator. In the plant shown here a so-called high pressure evaporator (29) with heating element (28) is provided for expelling the major .part of the sulphur dioxide from the extract solution before the latter enters condenser .pressure evaporator (42). The pressure of. the extract solution entering high pressure evaporator (29) is regulated by throttle valve (27). The sulphur dioxide vapors expelled in evaporator (29) are partly used as heating medium in heating device (40) of'condenser pressure evaporator (42), and are partly .conducted through pipes (30),;(31) and (32) to distillate preheater (2) and liquid sulphur dioxide preheater (8), where they are condensed, thereby giving up their latent heat to the untreated oil and sulphur dioxide respectively. The collected condensates flow under their own pressure through pipes (33), (34) and (35) to cooler (37). entering this cooler they join the sulphur dioxide liquid coming from vapor heater through pipe (36). The assembled liquefied high-pressure sulphur dioxide is cooled down in cooler (37) and then flows through throttle valve (38) into the liquid sulphur dioxide collector (6) from where it is recycled into the process.

The extract solution, after having passed high pressure evaporator (29), flows through throttle valve (39), sulphur dioxide vapor heater (40). steam heater (41), to evaporator (42). The sulphur dioxide vapors expelled in this pressure stage leave evaporator (42) through pipe (43), and areled to condenser (5) through pipes (45) and (46) after having been united with the sulphur dioxide vapors of pipe (44). From the condenser pressure evaporator (42) the extract solution flows with but a relative small sulphur dioxide content through throttle valve (47) heat- Before ing device (48) into evaporator (49). This evaporator is under the same low pressure as rafllnate evaporator (20). Due to the higher temperature and the reduced pressure the extract is freed from all but traces of sulphur dioxide. The expelled sulphur dioxide vapors are sucked up by gas pump (50) together with the vapors from railinate evaporator (20) and are led through pipes (51) and (46) to condenser (5). denser (5) the vapors are cooled and liquefied by cooling water and are then recycled into the process. The extract solution remaining in evaporator (49) is pumped by pump (52) through pipe (53) and heat exchanger (26) where it is partly cooled, thence to a finished extract tank (not shown here).

The above description and the fiow sheet shown here are supposed to be merely an example of .how the liquid sulphur dioxide hot extraction process may be carried out. A great number of modifications in the equipment and in the way of treating are possible, all falling within the scope of this invention.

I have found hot S02 extraction to be specially beneficial on heavy oils, but cases may arise where also lighter oil fractions are advantageously hot extracted, hence, it is not our intention to limit our new process to lubricating oils only.

As to the aftertreatment of the refined oils (raffinates) obtained with the liquid sulphur dioxide hot extraction process, any suitable treating methods are possible. With lubricating oil raffinates, good results have been noted on rerunning with or without vacuum and with or without alkali, but also clay treatment resulted in finished products of high quality.

Having described and illustrated my invention, but without any intent to be limited thereby, what I claim is as follows:

1. The process of refining petroleum lubricating oil fractions comprising extracting the fraction with liquid-S02 at a temperature above 85 F., the temperature and pressure being such as to maintain the solvent SO: in the liquid phase, said extraction producing a higher quality lubricating oil than can be obtained by extracting with cold liquid-S02. I

2. The process of refining petroleum lubricating oil fractions comprising extracting the fraction with liquid-S02 at a temperature of 85-200 F., and under a pressure at least suflicient to maintain the solvent SO: in' the liquid phase, said ex-.

traction producing a higher quality lubricating oil than can be obtained by extracting with cold liquid-SOz.

3. The process of refining heavy mineral oils containing considerable quantities of undesirable constituents, comprising extracting the oil with liquid-S02 at a temperature above 85 F., temperature and pressure being such as to maintain the solvent S02 in the liquid phase.

4. 'The process of refining heavy mineral oils containing considerable quantities of undesirable constituents, comprising extracting the oil with liquid SOz at a temperature of 85-200 F. and

In con-' under a pressure at least suflicient to maintain the solvent SO: in the liquid phase.

5. The process of refining heavy mineral oils and petroleum lubricating oil fractions comprising mixing the fraction with liquid-S02 at a temperature above 85 F., the temperature and pressure being such as to maintain the solvent SO: in the liquid phase, allowing a separation into a raflinate layer and an extract layer, dividing out the two layers, removing the SO: therefrom, and

,eeetese after-treating the ralrzate as desired t0 see e the final refined oil.

6. The process of refining heavy mineral oils and petroleum lubricating oil fractions eompris= ing mixing the fraction with liquid-S02 at a temperature of S5-200 F. and under a pressure least sufiicient to maintain the solvent $62 the liquid phase, allowing a separation into a re ate layer and an extract layer, dividing eut the two layers, removing the S02 therefrom, and after-=- treating the raffinete as desired to secure the final refined oil.

7. The process or" refining petroleum lubrieat= Eng eii fractions comprising extracting the fraction by the counter-current method with liquid- SS2 at a temperature above 85 the temperaanti pressure being such as to maintain the selvent $02 in the liquid phase.

8. The process of refining petroleum lubricating oil actions comprising extracting the fraction by the counter-current method with liquid-S02 at a temperature sf 85-2i30 F. and under a pressure at least sufficient to the solvent $02 in the liquid elaasee EGNAZ ROSENBERG. 

